/* origin: FreeBSD /usr/src/lib/msun/src/e_asinl.c */
/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunSoft, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */
/*
 * See comments in asin.c.
 * Converted to long double by David Schultz <das@FreeBSD.ORG>.
 */

#include "libm.h"

#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
long double asinl(long double x) {
  return asin(x);
}
#elif (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384
#include "__invtrigl.h"
#if LDBL_MANT_DIG == 64
#define CLOSETO1(u) (u.i.m >> 56 >= 0xf7)
#define CLEARBOTTOM(u) (u.i.m &= -1ULL << 32)
#elif LDBL_MANT_DIG == 113
#define CLOSETO1(u) (u.i.top >= 0xee00)
#define CLEARBOTTOM(u) (u.i.lo = 0)
#endif

long double asinl(long double x) {
  union ldshape u = {x};
  long double z, r, s;
  uint16_t e = u.i.se & 0x7fff;
  int sign = u.i.se >> 15;

  if (e >= 0x3fff) { /* |x| >= 1 or nan */
    /* asin(+-1)=+-pi/2 with inexact */
    if (x == 1 || x == -1)
      return x * pio2_hi + 0x1p-120f;
    return 0 / (x - x);
  }
  if (e < 0x3fff - 1) { /* |x| < 0.5 */
    if (e < 0x3fff - (LDBL_MANT_DIG + 1) / 2) {
      /* return x with inexact if x!=0 */
      FORCE_EVAL(x + 0x1p120f);
      return x;
    }
    return x + x * __invtrigl_R(x * x);
  }
  /* 1 > |x| >= 0.5 */
  z = (1.0 - fabsl(x)) * 0.5;
  s = sqrtl(z);
  r = __invtrigl_R(z);
  if (CLOSETO1(u)) {
    x = pio2_hi - (2 * (s + s * r) - pio2_lo);
  } else {
    long double f, c;
    u.f = s;
    CLEARBOTTOM(u);
    f = u.f;
    c = (z - f * f) / (s + f);
    x = 0.5 * pio2_hi -
        (2 * s * r - (pio2_lo - 2 * c) - (0.5 * pio2_hi - 2 * f));
  }
  return sign ? -x : x;
}
#endif